In wireless communication systems which provide two or more different services, if the services are sufficiently dissimilar, a substantially independent network is provided for each service, resulting in a system with multiple networks. An example of a system providing multiple services is the iDEN™ system of Motorola™ which provides dispatch services including push-to-talk™ (PTT™), and interconnect services for regular phone call services. Although independent in the sense that they provide different services, the networks of a multiple network system may share various hardware and software resources as required. For example, in the iDEN™ system, the dispatch network providing the dispatch services and the interconnect network providing GSM-like telephone services share EBTSs (Enhanced Base Transceiver Stations), cells, and various other resources.
Paging mobile devices registered on a network but idle when paged uses network resources. If the location of a mobile device were completely unknown, in order to ensure that the mobile device is paged, all of the cells of the entire network (from which the page originated) would be used to page the mobile device. This uses valuable network resources.
To increase mobile device paging efficiency, typically for each network in a wireless communication system, cells are grouped into logical areas. The mobile device and the network tracks the particular area(s) in which the mobile device is or most recently was located by having the mobile device update, in the network, a log of the mobile's location whenever it crosses into a new logical area. When a page over a service associated with a particular network is to be transmitted, only those cells in the area in which the mobile device is most likely located are paged, efficiently ensuring a level of certainty that the mobile device is paged. The cost of paging a mobile device which is registered on a network but is idle when paged, is reduced because not all of the cells of the network are used to page the mobile device. Moreover, since the mobile device updates the network of the logical area into which it crosses every time it crosses a logical area boundary, having a logical area made up of one cell is wasteful of both network resources and the mobile device's battery. Accordingly, a logical area of a size less than the entire network but larger than a single cell is typical.